Canon FY8-13EX-000, NP6218 service manual Turning On and Off the Primary Charging Roller Bias, 4-11

CHAPTER 4 IMAGE FORMATION SYSTEM

2. Turning On and Off the Primary Charging Roller Bias

The microprocessor (Q512) on the composite power supply PCB generates the PDCPWN signal (pulse signal) under the control of the microprocessor master (Q301) on the DC controller PCB. In response to the signal, the secondary side of the main transformer (T101) turns on to apply a primary charging roller bias.

The main transformer (T101) is driven by the drive signal (MPWM) from the microprocessor (Q512). The main transformer (T101) is also used as the high-voltage transformer for the DC power supply and other loads.

3. Controlling the Primary Charging Roller Bias to a Constant Voltage

While a bias voltage is being applied to the primary charging roller, the microprocessor (Q512) on the composite power supply PCB reads the PDCS signal (analog signal) from the voltage detection circuit to control the PDCPWM signal so that the output voltage is maintained at a specific level.

4. Switching the Primary Charging Roller Bias Application Voltage Level

The copier applies a cleaning bias to the transfer roller during initial rotation (INT), while the scanner is moving in reverse (SCRV), and during last rotation, thereby cleaning the transfer charging roller. (See p. 4-21.)

To enhance the result of cleaning by the cleaning bias and to prevent drum memory caused by the cleaning bias, a cleaning primary charging roller bias is applied during initial rotation and while the scanner is moving in reverse.

COPYRIGHT © 1997 CANON INC. CANON NP6218 REV. 0 MAY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON) 4-11